National productivity and IQ
Turns out they are highly correlated:
My colleague at the George Mason economics department, Garett Jones, has written an excellent new book, Hive Mind: How Your Nation’s IQ Matters So Much More Than Your Own.
The book’s primary and most important contribution is to document the following empirical regularity: Suppose you could a) improve your own IQ by 10 points, or b) improve the IQs of your countrymen (but not your own) by 10 points. Which would do more to increase your income? The answer is (b), and it’s not even close. The latter choice improves your income by about 6 times more than the former choice.
The only thing surprising about these results is that someone was actually allowed to publish them.